Magnetic resonance imaging and positron emission tomography are being used to assess neuroanatomy and brain function in normal controls and subjects with developmental disorders. Diagnostic groups involved in the studies include attention deficit hyperactivity disorder, autism, childhood onset schizophrenia, dyslexia, multi-dimensional impairment syndrome, obsessive compulsive disorder, stuttering, Sydenham's chorea, and Tourette's syndrome. The normal controls serve as a comparison group for the developmental disorders and to examine normal development and gender differences in children and adolescents. To date, MRI findings suggests smaller area measurements of the rostrum and rostral body of the corpus callosum in ADHD patients and increased ventricular size and decreased temporal lobe volume in childhood onset schizophrenics. MRI regional brain volume and corpus callosum studies of gender differences in normal development reveal a surprising convergence of structure size at puberty, instead of the anticipated divergence. Sydenham's chorea patients demonstrate quantifiable changes in caudate nucleus morphology which seem to fluctuate with the severity of symptoms. O-15 PET and functional MRI studies of remediated dyslexia are currently underway to test the dual-route theory of reading.